摘要
In this study, we report the effect of temperature on the microstructural evolution of flip chip solder joints under a temperature gradient of 2580 °C/cm at ambient temperatures of 100 °C, 125 °C, 150 °C, 160 °C, and 175 °C. The experimental results show that no microstructural evolution of un-stressed solders was found for samples tested at ambient temperatures of 100 °C and 125 °C, whereas thermomigration induced phase separation was observed for the samples tested at 150 °C, 160 °C, and 170 °C, suggesting that the thermomigration only occurred when the ambient temperature was higher than 150 °C. The theoretical derivation indicates that the threshold temperature difference needed to trigger thermomigration is found to be decreased with an increase in the ambient temperature. In addition, at a temperature gradient of 2580 °C/cm, the theoretical calculation indicated that a threshold temperature to trigger thermomigration is about 150 °C.